You know I hesitate to say anything since I live in the South
but my chicks were without their light (heat) from 5 1/2 weeks on and they were living on the screened porch. It was still getting into the 40s at night at that time. They were protected from drafts by a good draft guard.
Now they are the hardiest bunch of chickens you've ever seen.
I'm at this point with my chicks too. They are out in the garage now. I have a 200w light bulb on them still since the garage isn't insulated and it is damp without the light drying out the area. However yesterday, late afternoon, my bulb went out and I didn't notice it until about 11pm when I went out to do last feeding and water. It was in the high 30s in the garage when I got out there and all was quiet. I was so worried. It ends up the bulb just got loose so I screwed it back in and all the chicks were just sleeping. They weren't puffed up or anything. After the light came back on they didn't bother to collect under it either. I'm thinking mine are about ready to go without but I am not sure I'm ready to let them go without
I'm hoping to integrate them into the coop end of next week though and they will be w/o light out there since I have no power out there. They are completely feathered now so I guess I'm just stalling for myself.
Just an update.....it was down to about 38 here last night and all survived LOL. Actually I went out there every few hours (I was up till 3am anyway
) and they weren't even in their house....they were all lined up on the roost together. There was no breeze at all, so they did well.
Now today we've got 50+mph winds and it's COLD, so they're running in and out of their house playing, but still no lamp. And I KNOW their house is completley sheltered from the wind, insulated, and bedded deeply. No more lamp for them
Plus, I needed their lamp for new chicks I got yesterday ROFL
I must be babying my chicks by leaving the heat lamps on. When I went out to check on them the second night in their coop at sunset and they were all huddled in a corner of the coop, I thought they needed the lamps.
Turned on the lamps and they then went and slept in the brooder the last two nights which tells me they want the heat.
Monday and Tues it got down in the 30's - last night 40's.
I have my heat lamp cords wrapped around things twice and chain attached to the hangers so they aren't going anywhere if something should hit them.
but my chicks were without their light (heat) from 5 1/2 weeks on and they were living on the screened porch. It was still getting into the 40s at night at that time. They were protected from drafts by a good draft guard. 
